Storm King®
Dynamic Wet Weather Separator
Columbus, GA
Storm King® satellite treatment significantly reduces project costs.
Wet Weather Case Study - Project Profile
Objective
Project Highlights
In partnership with the client, the engineer and the community
help turn an unfunded mandate into the future of CSO treatment
technology.
•• The final solution included 12 Storm King® separators, 28 HydroBrake® vortex valves and 3 Grit King® separators at two locations
on the Chattahoochee River
Solution
•• $20-30 million project savings
Developed an innovative solution based on satellite treatment using
Storm King® Separators at two CSO locations, showing significant
cost reductions.
•• The project won Columbus Water Works the 2001 EPA Award
for CSO Program Excellence
The City of Columbus, GA knew firsthand the pollution problems
that combined sewer systems caused. In dry conditions, the city’s
combined sewer overflows (CSOs) were not a problem, but during
heavy rain events the rapid influx of stormwater caused the system
to overload — resulting in untreated water to flow directly into the
Chattahoochee River. The river provides drinking water for over
half of all Georgians and recreational opportunities for more than
25 million people each year.
Using a traditional wastewater treatment approach would have
required an extremely large and expensive facility.
Not only did the overflows cause exceptionally high fecal coliform
levels in the hundreds of thousands of colony forming units (CFU),
they also discharged aesthetic pollutants directly into the river.
“It was not unusual to see the river covered shore to shore with
floatable materials,” said Cliff Arnett, Senior Vice President for the
Division of Water Resource Operations, Environmental Compliance
and Managed Maintenance at the Columbus Water Works.
With the help of a $20 million appropriation from Congress and the
U.S. Environmental Protection Agency, the Columbus Water Works
was able to implement a CSO control program that encompassed
a technology demonstration site. The agency evaluated 44 different
options to determine the most cost effective and meaningful way to
address more than 5,200 acres served by combined sewers in the
downtown area of Columbus.
Alternatively, the agency could separate all of the sewer and
stormwater lines, but this would also have cost hundreds of millions
of dollars and caused major disruptions across the city while roads
were torn up to separate the sewers. “The cost of separation is
extravagant, and it completely interferes with the normal operation
of the city,” Arnett said. “While we did separate two relatively small
sub-basins we didn’t feel that was a good approach for the bulk of
our CSOs.”
The engineering firm, Parsons Engineering Science, approached
the agency about using vortex separator units. Thanks to a
grant from the Water Environment Federation, along with capital
donations from private and municipal entities, the agency was able
to test out the vortex separators. The Water Works set up a pilot
test on the banks of the Chattahoochee River to evaluate the vortex
separators side by side with the traditional treatment approach.
The agency discovered half of the area already had its own
separate stormwater sewer, but that it had been flowing into the
combined sewer area. To resolve this problem, the Water Works
installed an interceptor to redirect the flow to the wastewater
treatment plant. However, this still left approximately 2,600 acres in
a highly urbanized area to be addressed.
“We’re saving an estimated $20-30 million
in capital costs alone.”
- Cliff Arnett, Senior VP for the Division of Water Resource
Operations, Environmental Compliance and Managed
Maintenance at the Columbus Water Works
www.hydro-int.com Storm King® overflow vortex separators provide a cost effective,
sustainable solution for the City of Columbus, GA
Tel: (866) 615 8130
Numerous organizations, including Parsons Engineering Science,
the Water Environmental Research Foundation, and Trojan
Industries (a manufacturer of ultraviolet disinfection technologies)
supported the pilot project.
“One of our major concerns was whether the vortex separators
could remove solids and that there was sufficient contact time
within the separator to accommodate disinfection,” Arnett said.
“This had never been done before. We were pleased to discover
that the vortex separators could remove solids equivalent to a
horizontal settling basin, and did indeed have enough contact
time for disinfection - in roughly one tenth of the footprint of a
conventional plant. This meant we were looking at significant
savings. In addition, the filter operates at very high flow rates,
which is ideal for stormwater problems.”
Based on the impressive results, the Columbus Water Works
built two wet weather treatment plants, one on the upper end
of the system and another on the lower end. Water flows from
the combined sewer system to the two satellite wet weather
treatment facilities where a portion of the flow is directed to the
main wastewater treatment facility before flow is introduced into
the facility. Wet-weather treatment involves three primary steps:
physical separation of solids from the waste stream, removal of
organic materials from the waste stream, and reduction of bacteria.
Storm King® units are advanced hydrodynamic vortex separators
that augment gravitational forces to separate solids from water.
The flow swirls through circular tanks, which separate concentrated
solids to the bottom. These vessels have no moving parts, reducing
maintenance issues.
“Stormwater picks up a tremendous amount of grit and gravel in
the runoff process,” Arnett said. “Sand and grit are enemies in a
stormwater system. They cause wear and tear and clog sewers.
That’s always been a problem here in Columbus, requiring the
sewer lines to be cleaned every two years. Using the Grit King®
eliminates this problem altogether.” For this reason, Grit King®
separators were installed in conjunction with the Storm King® to
remove grit at the satellite facility as opposed to transporting it
through miles of pipe to the wastewater treatment plant.
After grit is removed, water flows into a secondary Storm King®
where it is treated with sodium hypochlorite within the vortex
separator in tandem with UV disinfection after filtration to virtually
eliminate all pathogens. This vortex separator (which now
incorporates Swirl Cleanse screening technology) enables water to
be treated in much less time than in conventional systems.
In extremely heavy rainstorms, water flow is controlled using
Hydro-Brake® Vortex Valves. Designed with a conical shape, a
Hydro-Brake® vortex valve restricts the flow of water as needed.
As flow increases, an air core, accompanied by substantial
backpressure, chokes the flow through the outlet aperture. Using
this approach, the Columbus Water Works was able to significantly
enhance flow handling capacity with no additional equipment.
The entire system is automated. Rain sensors alert the treatment
system when it needs to be initiated. The cost savings have been
enormous. “We’re saving an estimated $20-30 million in capital
costs alone,” Arnett said. “Plus, since the system is unmanned,
it’s extremely easy and economical to operate. Our consulting
engineers estimated that this technology could save billions of
dollars if all cities across the country used it.”
To ensure the system was working to maximum efficiency, the
agency conducted extensive water quality analyses to understand
resulting pollutant loads. Test results confirmed that the new
system reduced bacteria levels to less than 100 CFU per 100 ml,
from a high of over 100,000 CFU per 100 ml.
“As a wastewater utility, we believe in being good stewards of the
environment,” Arnett said. “As part of our program, we redeveloped
the river interceptor, a 96-inch diameter sewer along the edge of
the river. This included
building a showplace
river walk transforming
a blighted area of
downtown Columbus into a
magnificent place.”
The EPA granted the
agency a post-Phase II
Piloting on the banks of the Chattahoochee
River helped Columbus evaluate Hydro
NPDS permit verifying that
International’s vortex separator as an
it is in total compliance
alternative to conventional options
with stormwater treatment
regulations, and honored
the agency with the 2001
EPA Award for CSO
Program Excellence. Since
that time, the Columbus
Water Works has gained
worldwide recognition
for the project — serving
as a model for cleaner
communities.
Hydro International. 2925 NW Aloclek Suite 140. Hillsboro, OR 97124. Tel: (866) 615 8130
Email: [email protected] Web: www.hydro-int.com
Storm King® - Columbus, GA - Case Study - V16.1
The Grit King® vortex separator removes
“We’ve made presentations sand and grit from the flow stream helping
in the United Kingdom,
protect downstream infrastructure from
Japan, Brazil – you name
wear and tear as well as clogging
it,” Arnett said. “People
from Mexico, India, Russia,
Japan, South Korea,
Australia, New Zealand and
Hong Kong have all come to
visit, too. We took a chance
on a leading-edge solution
based on vortex technology,
Entrance to underground facility where
and we’re happy to show
Storm King® units provide a sustainable
whoever’s interested that it
solution for CSO treatment
passed with flying colors.”
The river walk in Columbus has become
a popular destination for residents and
tourists to enjoy the Chattahoochee River
Wet Weather Solutions
Turning Water Around...®